Pump heat radiation shield



2 Sheets-Sheet 1 INVENTOR THU/VAS N. H/C/(EY awww A 7' TORNE YS March 3, 1964 T. N. HxcKEY PUMP HEAT RADIATION SHIELD Filed oct. 51, 1962 M LIII United States Patent O 3,?229l5a`6 lUMP HEAT lADlAlN SHHELD Thomas i* Hickey, Qolumbns, Ohio, assigner to tryovac, hac., Columbus, Ohio, a corporation oi' Ohio Filed Oct. 3l, 1962, Ser. No. 216,6@4 12 Claims. (Cl. 632-259) This invention relates generally to space simul-ation chambers and particularly to an improved thermal shroud and baille construction for shielding a test specimen mounted within the chamber from the dilusion pump used to evacuate the chamber.

in general, space simulation chambers are employed in the space vehicle program to simulate the cold black environment of outer space. ln construction, they include a sealed outer chamber that is evacuated by a diffusion pump and a thermal Shroud comprising a refrigerated wall forming a heat sink is mounted within the outer chamber and cooled by conduits containing ilowing cryogenic gas.

ln instances where gaseous helium is used as a refrigerant the thermal shroud temperatures are in the range of 15 to 2O degrees Kelvin.

A typical thermal shroud construction is illustrated and described in detail in my co-pending application Serial No. 216,625 filed October 3l, 1962.

In accordance with the present invention, one wall of the thermal shroud, for example the bottom wall, as illustrated herein, is provided with a shroud opening that confronts the inlet of a conduit leading from the sealed outer chamber to a diilusion pump used to exhaust the chamber to an extremely high degree of vacuum.

In accordance with the present invention, the above mentioned opening in the wall of the thermal shroud is provided with an optically tight shroud wall baille means of high refrigeration capacity forming a pervious wall that is finished in ilat black on the inner side that confronts the test specimen to simulate the infinite heat sink conditions of outer space.

As another aspect of the present invention a backstrearn prevention baffle means of relatively low refrigeration capacity is located within the passage leading to the diffusion pump and serves to prevent oil vapour from the diiusion pump from baclostream into the test charnber which is actually maintained at a lower pressure than the diffusion pump. The back-stream prevention baille means is cooled by an annular manifold for conducting a llow of refrigerant in the form of a cryogenic gas such as liquid nitrogen.

As still another aspect of the present invention the conduit leading to the inlet of the diffusion pump is provided with a novel water-cooled spiral baille means located outwardly of the back-stream prevention baille means that forms an optically insulated cool wall which protects the bacrstrearn prevention baille means from high temperature radiation from the hot inlet of the diffusion pump.

t is, therefore, an object of the present invention to provide an improved thermal shroud and cryogenic baflle construction that provides a diffusion pump penetration for the thermal shroud that maintains across its area substantially the same heat sink characteristics of the thermal shroud.

It is another object of the present invention to provide an apparatus of the type described that includes an inner shroud wall baille means that presents to a diilusion pump an optically tight wall to pump through and which, at the same time shields a second back-stream prevention baille Patented lll/lar. 3, ld-

an apparatus of the type described that incorporates an optically tight baille Wall for a thermal shroud that prevents oil from a diffusion pump from migrating up into the confines of the thermal shroud.

lt is another object of the present invention to provide a thermal shroud and baille construction that permits operation of a diffusion pump at pressures above pressures existing within the confines of the thermal shroud.

It is another object of the present invention to provide an improved themal shroud and baille construction that incorporates a novel water-cooled spiral baille adapted to shield a back-stream prevention baille means from direct radiation from the hot inlet to the diffusion pump.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred form of embodiment of the invention is clearly shown.

In the drawings:

FIG. 1 is a broken perspective view of a typical space simulation chamber that incorporates the thermal shroud and baille construction of the present invention;

PIG. 2 is a side sectional View showing the apparatus of FlG. l; and

FlG. 3 is an enlarged view of a back-stream prevention baille means and spiral baille means assembly constructed in accordance with the present invention.

Referring in detail to the drawings, a space simulation chamber is indicated generally at Ztl and includes an outer structural wall 22 that forms a sealed chamber 24, said chamber being evacuated by a diffusion pump the intake of which is indicated at 25.

A thermal shroud indicated generally at 2S is mounted within structural wall 22 and includes a refrigerated wall 3o that is cooled by conduit means 23 in heat exchange relationship with the wall that carries a ilow of liquid nitrogen. Conduit means 23 is shown in the form of tubes integral with wall 3o and includes a refrigerant inlet 25 and a refrigerant outlet 27 connected with the refrigerating means, not illustrated.

Cryogenic shield 28 is suspended within the container means by appropriate structure of the type described in detail in my co-pending application Serial No. 216,625 lled October 3l, 1962.

As is best seen in FlG. 2, the bottom oi the thermal shroud 28 includes a shroud wall baille means indicated generally at 32 that comprises side frame member 34 that supper' s a plurality of transverse baille members 36 of tf-shaped cross section, said cross sectional coniiguration being illustrated in FIG. 2. Each of the battle members 36 is cooled by coolant conduits 37 that carry a flow of liquid nitrogen. The wall Sil of shroud 28 is also cooled by conduits contmng liquid nitrogen, not illustrated. This wall construction is described in detail in my copending application Serial No. 216,625, filed October 3l, i962.

A conduit .3S connects the interior of space chamber 2o with the previously mentioned inlet 26 of the diffusion pump and includes an inlet portion in which is mounted a back-stream prevention baille means indicated generally at itl that comprises an annular manifold 4.12.

`inlet conduit 44 is connected to manifold l2 at a fitting 46 and passes outwardly through the wall of conduit 33 at Va fitting 48.

The ilow of liquid nitrogen is released from manifold 42 via a conduit Si) that is connected to the manifold at a iltting S2 and which passes outwardly through the wall 33 of the conduit at a fitting d3.

As is seen in FiG. 3 manifold 42 is mounted -to the means, located outwardly from said shroud wall baille Conduit Wall 33 by an annular hanger bracket 54,

means, from hot radiation from a specimen in the shroud.

lt is another object of the present invention to provide Referring again to FIG. l, a water-cooled spiral baille eans is mounted between liquid nitrogen cooled baille S Il and the inlet 26 of the diffusion pump and is indicated generally at et?.

The spiral bafrle means 69 comprises a narrow continuous strip of' metal, such as copper or the like, that is preferably cut from sheet stock and stretched out to the conilguration seen in FiGS. l and 3.

This spiral strip of metal is indicated at o2 and is supported by a rack formed by a plurality of inclined members 64', the inner edges of which are provided with notches 66 that form horizontal edges that support strip 6".

As is seen in FlG. 3, inclined members 64 are mounted to the cylindrical wall 3S' of the conduit by a plurality of inwardly extending brackets 7G.

The spiral metal strip 162 is cooled by a continuous length of tubing 72 mounted on the upper surface thereof for conducting a flow of coolant, `such as water, in heat exchange relationship with the strip.

Coolant conduit 79 includes inlet portion 7d and outlet portion Y76 that cormect the spiral tube 72 with a coolant circulation system not illustrated.

ln operation, a test specimen indicated generally at ll), which lmay in the form of a space vehicle or other object to be tested, is supported within the contines of thermal shroud 28,` as seen in FlG. 2.

The chamber within shroud 28 is cooled down by a cryogenic refrigerator which supplies a llow of refrigerant, such as liquid nitrogen, in heat exchangev relationship with wall 3G the thermal shroud 2S which functions as a heat sink for absorbing radient energy from test specimen l?.

The chamber is evacuated by operating the diffusion pump, not illustrated, which withdraws gases from the interior of the chamber Wall 22 and thermal shroud 2S.

y1t should be stated generally that dillusion pumps used for evacuating space chambersk operate on the oil jet principles and at oil vapor pressures in the neighborhood of 1 16 millimeters of mercury at the pump. By incorporating the baille construction of the present invention it is possiblerto operate the system with a pressure dillerential between the pump and the chamber 2d within the shroud such that the pump operates at a higher pressure than the extremely low pressure value required within the space chamber'.

When the diffusion pump is being operated, the backstream prevention means 4@ provides a shield that prevents back-streaming of oil from pump 26 to test chamber 24.

The shroud wall baille means 32 provides an optically tight cold wall that maintains shroud wall heat sink characteristics across the diffusion pump penetration area.

Spiral baille means dil-'is operated by circulating water through the spirally wound tube 7 d in heat exchange relationship with the spiral metal strip 62, the latter serving to optically insulate back-stream prevention means di) from the radiation from the hot intake 260i the didusion Pu'mll it should be pointed out that the spirally extending metal strip o2 is arranged so thatV the inner edge of each coil overlaps the outer edge of the next preceding coil to provide it optically insulating configuration.

While the form of embodiment of the present invention as herein disclosed constitutes a preferred form, it is to be understood that other founs might be adopted, all coming within the scope of the claims which follow.

l claim: Y

l. An improved space simulation chamber comprising, in combination, an outer sealed chamber; refrigerated wall means forming a thermal shroud within Said sealed chamber for enclosing a test specimen and including an open wall portion; a cryogenically cooled shroud wall Y battle means for said open wall portion; a dilusion pump including an inlet opening; conduit means connecting said outer chamber with said inlet opening of said d-liliusion pump; a back-stream prevention baille means between said shroud wall baille means and said pump inlet openwherein said b a cooling 4manifold for a flow of liquiiled .cryogenic gas.

3. rhe improved space simulation chamber of claim l wherein said third baille means includes la condu-it for a ilow of coolant.

4. The improved space simulation chamber of claim l wherein said back-stream prevention baille means includes a cooling manifold for a iloW of yliquilled cryogenic gas and wherein said third baille means includes a conduit for a flow of coolant.

5. The roved space simulation chamber of claim 1 wherein said third baille means includes a spiral strip, the diameter of said spiral being progressively greaterY in an axial direction; and a spiral conduit carried by saidl strip nor conducting a flow of coolant along said strip.

6. rl`he impro-ved space simulation chamber of claim l wherein said back-stream prevention baille means includes a cooling manifold for a llow of liquirledV cryogenic gas and wherein saidthird baille means includes a spiral strip, the diameter "or" said spiral being progressively greater in an axial directionyand a spiral conduit carried by said strip for conducting a ilow of coolant along said strip.

7. An improved space simulation chamber' comprising, in combination, an outer sealed chamber; refrigerated wall means forming a lthermal shroud within said ealed chamber for enclosing a test specimen 'and including an openL wall portion; a shroud wall baille means for said open wall portion and including a plurality of transverse baille members oi kl-shaped cross sectional contiguration; a diffusion pump including an inlet opening; conduit means connecting said outer climber with said inlet opening of said diffusion pump; back-stream prevention baille means between said shroud wall baille means and said pump inlet opening; and a third baille means between said bacli-stream prevention baille means and said pump inlet openinv.

8. rr'he irnproved space simulation `cham-ber of claim 7 wherein said back-stream prevention baille means includes a cooling manifold for a ilow of liquilled cryogenic gas.

9. The improved space simulation chamber of claim 7 wherein said third baille means includes a conduit for a llow or" coolant.

il). The improved space simulation chamber of claim 7 wherein said back-stream prevention baille means includes a cooling manifold for a llow of liquiled cryogenic gas and wherein said third baille means includes a con-V duit for a flow of coolant.

ll. lhe improved space simulation chamber 'of claim 7 wherein said back-streamprevention baille means iai cludes a cooling manifold for a ilow of liquied cryogenic gas and wherein said third baille means includ a spiral strip, the diameter of said spiral being progressively reater in an axial direction; and a spiral conduit car` References Cited in the ille of this patent UNTED ST TES PATENTS 2,831,549 Alpert Apr. 22, 1958 2,934,257 Power Apr. 26, 196() 3,981,668 Milleron Mar. l2, 1963 PGEElGN PATENTS 1,971,89b` Germany Dec. 24, 

1. AN IMPROVED SPACE SIMULATION CHAMBER COMPRISING, IN COMBINATION, AN OUTER SEALED CHAMBER; REFRIGERATED WALL MEANS FORMING A THERMAL SHROUD WITHIN SAID SEALED CHAMBER FOR ENCLOSING A TEST SPECIMEN AND INCLUDING AN OPEN WALL PORTION; A CRYOGENICALLY COOLED SHROUD WALL BAFFLE MEANS FOR SAID OPEN WALL PORTION; A DIFFUSION PUMP INCLUDING AN INLET OPENING; CONDUIT MEANS CONNECTING SAID OUTER CHAMBER WITH SAID INLET OPENING OF SAID DIFFUSION PUMP; A BACK-STREAM PREVENTION BAFFLE MEANS BETWEEN SAID SHROUD WALL BAFFLE MEANS AND SAID PUMP INLET OPENING; AND A THIRD BAFFLE MEANS BETWEEN SAID BACK-STREAM PREVENTION BAFFLE MEANS AND SAID PUMP INLET OPENING. 